I’m a big fan of WordPress Multisite: I use it to manage a small network of client sites, hold all of my demo sites in one place, and also run a network allowing people to create their own custom sites.
So it’s always nice to see Multisite getting a bit of love when WordPress is updated. WordPress version 4.4 included some nice enhancements to Multisite, which are particularly useful if you’re customizing the signup process or working with options. Here’s an overview of them.
WP_Network has been added to make the way Multisite is set up tidier and better defined. It populates the $current_site and $current_blog globals.
If you’re manually populating those globals, or interacting with them in another way, you may need to test your code, although the core team have tested the changes to maximise backwards compatibility.